We propose to continue our basic research toward understanding membrane assembly and membrane protein-lipid interactions. Because of its simplicity of structure, the formation of the membrane-containing bacteriophage PM2 offers a unique system to focus on the molecular basis fo membrane biogenesis and interaction of membrane proteins with membrane lipids. In particular, we ask the question, "What controls the size, shape and composition of a biological membrane?" A multidisciplinary approach toward answering this question has already begun to yield important results. The power of bacteriophage genetics involving conditional-lethal membrane mutants is utilized in order to dissect the control of membrane biogenesis and membrane protein-lipid interactions. Results to date characterizing mutant ts 1 of PM2 indicate that the 6,600 dalton structural protein of the virus may contain the information required for making a membrane of the desired size, shape and composition. Further characterization of defective membrane vesicles made inside infected cells by similar mutants will confirm that this protein is what controls membrane biogenesis. The construction of a Pseudomonas BAL-31 host bearing a suppressor will permit the isolation of amber mutants of PM2. Biochemical studies of the assembly of the PM2 membrane will proceed by radio-labeling viral proteins as they are synthesized and determining their temporal associations with the host membrane. Membrane morphogenesis will be studied by electron microscopy of membranes of infected cells labeled with ferritin-conjugated antibodies to the viral structural proteins. The physical-chemical basis for membrane assembly will be determined by examining the phospholipid binding specificity of an integral membrane protein of PM2. These multiple approaches synergistically complement each other toward understanding, for the first time, the genetic, biochemical and physical principles underlying the biosynthesis, assembly and morphogenesis of a biological membrane.